The present invention relates to power transmission mechanisms, and more particularly to frictional drive systems providing a wide range of ratios of rotation between input and output in which the ratio is continuously variable and controlled by the applied input torque for bicycles, motorcycles, and the like.
In power transmission applications wherein it may be desirable to alter the drive ratio, especially in motorbikes and bicycle transmissions, it is common practice to employ a plurality of gears and gear shifting components which are costly and failure prone. For optimum efficiency, riders may prefer to apply a constant pedal force, whereas the terrain may require more or less energy to traverse, depending on grade. To achieve this goal of constant pedal force, the rider continuously shifts gears. In order to keep the incremental change between gears small, a greater number of gears is required and a greater number of shifting actions are required with energy loss at each shift. The rider is also distracted from the cycling effort by the manual shifting operation. Despite numerous efforts to overcome these deficiencies, the cycle industry is currently producing bicycles with few or many gears and the consumer is burdened with high maintenance costs, abrupt ratio changes and multiple shifting efforts.